Sheet-fed Offset Printing
The sheetfed-offset prinitng is a indirect process, which is most common in the fields of book-, newspaper-, commercial-, label- and packaging printing.
Sheetfed offset print means that you do not print directly onto the paper, but on a interjacent rubber roller, which applies the colour onto the paper.
This technique is also called flat or surface printing: the printing plate does not have any deepening or height. A special surface coating defines, which parts of the printing form are printed and which not. Before the print, the printing plate will be covered with water. The water adheres at those points, which should not be printed. It drains from the points which should be printed. After that, the colour will be applied onto the printing form. The colour does not adhere to those points, where water adheres. The colour adheres at those points, where no water adheres to the printing form.
After that, the colour will be applied from the printing form onto a rubber roller, the so-called blanket, which applies the colour onto the paper. Sheet-offsest presses get the paper via portioned sheet. These sheets are assorted as piles in the feeder. The so called gripper systems brings the sheet individually through the printing machine. The paper is printed in the printing machine and then piled again in the delivery.
Besides the speed of up tu 20.000 sheets/h, it is the reduced set up time which is most important especially for small runs. This saving of time can be achieved by important features such as automatic and simultaneous plate changing and washing systems. Computerized control units and in and offline measuring and control technology assure the qualtiy. The main manufacturers of sheetfed offset printing machines are MAN Roland, Heidelberg, KBA, Komori, Mitsubishi and Ryobi.